The invention relates to toothbrushes, and more particularly relates to powered toothbrushes. In its most immediate sense, the invention relates to a brush tip for a powered toothbrush of the type in which the motor moves a plurality of brush heads.
In a conventional motorized toothbrush of the multi-head type, a disposable brush tip is detachably secured to the handle of the toothbrush. The tip has a plurality of brush heads, which oscillate (as by rotation) under the power of the motor. Each brush head has a plurality of tufts of bristles.
Existing motorized toothbrushes have relatively small xe2x80x9ccoveragexe2x80x9d, i.e. they do not clean large surface areas at one time. This is because the brush heads are relatively small. If they are made too large, they will put an excessive load on the motor.
Furthermore, some users operate such toothbrushes improperly. Instead of applying only light pressure, they force the bristles hard against the teeth. Under such conditions, the distal end of each tuft of bristles stays in the same place and the tufts twist themselves tightly in alternate directions. This makes the brushing less effective, because the bristles do not scrub the surfaces of the teeth.
It would be advantageous to provide a multi-head motorized toothbrush that would have greater coverage than conventional toothbrushes.
It would also be advantageous to provide a multi-head motorized toothbrush that would perform better even when the user applies excessive pressure against the tooth surfaces to be cleaned.
In accordance with the invention, a brush tip for a motorized toothbrush has a first brush head and a second brush head. The second brush head encircles the first brush head, and means are provided for differently accelerating the first and second brush heads in response to motion produced by the toothbrush motor.
Because the second brush head encircles the first brush head, the two head together have a relatively large area and, therefore, greater coverage. And, because the two brush heads are accelerated differently, their bristles do not twist themselves together even when pressed hard against the teeth.
In preferred embodiments, the first and second brush heads are accelerated in opposite directions, the first brush head is circular, and the second brush head is elliptical. The elliptical brush head provides greater coverage than a circular brush head and the opposite motions of the heads make it impossible for the bristles attached to the first brush head to twist into the bristles attached to the second brush head.
For toothbrushes of the type wherein the motor produces oscillating rotational motion of a shaft, a gear is mounted at the end of the shaft and is used to rotate the brush heads. For toothbrushes of the type wherein the motor produces reciprocating linear motion of an actuator, two connecting rods are used to convert this linear motion into oscillating rotational motion of the brush heads.
Although the second brush head is advantageously continuous, it need not be so. It may be made up of a plurality of segments thereby having one or more gaps.